DALLAS, Texas (OSU Athletics ) - Oklahoma State's Shane Roller was named the first Big 12 Wrestler of the Week of the 2002-03 season, the conference announced Monday.    The two-time All-American received the honors after upsetting top-ranked Luke Becker of Minnesota, 9-5. Roller's decision propelled the top-ranked Cowboys to victory over third-ranked and two-time defending NCAA Champions Minnesota.    Roller has compiled a 12-2 overall record to date, while posting a perfect 5-0 dual record. He is currently ranked fourth in the latest Amateur Wrestling News rankings.    On Dec. 1, Roller also recorded another win against a Top 25 opponent. He recorded a takedown in sudden victory over Big 12 foe Kenny Burleson, giving him the 4-2 decision. Burleson was ranked No. 14 at the time.     Last season, the Bixby, Okla., native won All-America honors in the 157-pound division for the second straight year, after placing fourth at the 2002 NCAA Tournament and third the year before.    Roller and OSU return to action Sunday, when they host second-ranked Iowa at Gallagher-Iba Arena at 2 p.m.